The present invention relates to a conveyor system for transporting a vehicle skid. The invention further relates to the vehicle skid that is adapted for use in a conveyor system.
The body of a vehicle typically includes a large number of components that are assembled on a production line. These components can include a floor pan, stress-bearing panels for supporting suspension components, a passenger cage having A, B and C pillars, doors, as well as internal and external body panels. To increase production rates, assembly of vehicle bodies is becoming increasingly automated. Thus, a partially completed vehicle body is supported on a vehicle skid and passed down a production line between work stations at which various components are added to the partially completed vehicle body by robots. These robots include robots which accurately position components on the partially completed vehicle body, as well as welding robots to weld the components in place. At each work station, the vehicle skid is halted and lowered such that a reference hole in the partially completed vehicle body can be lowered around a reference pin associated with that work station. In this manner, the robot or robots at that work station know that the partially completed vehicle body is correctly positioned to allow the work at that station to be performed. Once the work at that station has been performed, the skid is raised so that the reference hole is raised clear of the reference pin and the skid is transported to the next work station.
Skids are generally transported between work stations using a conveyor system having a number of adjoining conveyor sections. Each conveyor section typically has a six meter long frame structure supporting a plurality of transversely extending shafts, with each shaft carrying a pair of support rollers. As is disclosed in EP-A-0 103 672 and EP-A-0 149 694, the transversely extending shafts may be driven by a common drive shaft to effect rotation of the support rollers. Alternatively, and as disclosed for example in EP-A-0 255 620, the transversely extending shafts may be driven by a drive belt arrangement. The support rollers contact support rails on the vehicle skid and friction between the rollers and rails causes the skid to be transported along the conveyor section.
In order that the partially completed vehicle bodies are correctly positioned at each work station, it is imperative that the conveyor system be able to stop the vehicle skid at a location with an accuracy of, for example, +xe2x88x923 mm. Furthermore, useful work is carried out on the production line only at the work stations. Thus, the transfer time between work stations should advantageously be kept to a minimum. Given that a typical skid weighs 120 kg before adding any body components, it will be appreciated that a great deal of inertia is involved in accelerating and deccelerating the skids. This characteristic is detrimental to the accuracy in trying to position the skid at each work station, particularly if the skids are transported between work stations at high speed.
It is an object of the present invention to provide a conveyor system that allows for shorter transfer time between work stations, but which nevertheless satisfies positional accuracy requirements.
Thus, since the drive means of a conveyor system that is configured in accordance with the present invention includes a drive belt having a toothed outer surface for engagement with a projection on the vehicle skid, an interlocking, rather than purely frictional engagement between the drive means and the skid is attained. This allows the skid to be subjected to greater acceleration and decceleration forces without loss of positional accuracy.
The invention further provides for a skid that is equipped with a suitable projection for engagement with the toothed outer surface of the drive belt of the conveyor system of the present invention.